With rapidly growing of user's needs for accessing digital contents everywhere, various communication technologies have been developed for transmission of the digital contents. These communication technologies may be developed for different environments, different transmission speeds and/or different user requirements. In addition, several medium access control (MAC) protocols are established based on different communication standards, which define different communication methods based on heterogeneous mediums. For example, IEEE 1901 communication standard is used for power line (PLC), IEEE 802.11 communication standard is used for wireless communication (i.e. WiFi), IEEE 802.3 communication standard is used for Ethernet, and Multimedia over Coax Alliance (MoCA) communication standard is used for coaxial cables, and so on.
As a result, a MAC abstraction sub-layer is developed for convergence of these various media. Please refer to FIG. 1, which is a schematic diagram of an exemplary communication device 10 in a data plane. The communication device 10 may be a mobile phone, laptop, tablet computer, electronic book, modem, or portable computer system, and uses various media for communication. In FIG. 1, the MAC abstraction sub-layer is arranged between an upper layer and a plurality of MAC types of a MAC layer each corresponding to a medium specification (i.e. PLC MAC, WiFi MAC, MoCA MAC, or Ethernet MAC). Each of the MAC types of the MAC layer includes a service access point (SAP), such that the MAC abstraction sub-layer can communicate with the MAC layer via the corresponding SAPs. The upper layer can be a network layer, a transport layer, an application layer or any layer responsible for processing the signalings and the packets received from the MAC abstraction sub-layer, and signalings and packets to be transmitted via the MAC abstraction sub-layer. In addition, the communication device 10 in the data plane includes a PHY layer with a plurality of PHY types. The plurality of PHY types of the PHY layer include an Ethernet PHY, an WiFi PHY, a PLC PHY and a MoCA PHY, which is complied with the IEEE 802.3 communication standard, IEEE 802.11 communication standard, IEEE 1901 communication standard and MoCA communication standard, respectively. Thus, the packet of the WiFi MAC, Ethernet MAC, PLC MAC or MoCA MAC can be received/transmitted through a corresponding PHY type of the PHY layer.
Further, the MAC abstraction sub-layer provides management functions (i.e. device management, or QoS negotiation) between communication devices. To implement management functions, communication devices should discover how many communication devices are in a network. However, there is no guideline for the device discovery mechanism, and therefore there is no device tables maintained for management frame exchange. In convention, the device table is provided in the communication device and includes at least two elements, device identity (hereafter called DID) and medium access control (MAC) address. By looking up the device table with the DID of a second communication device, a first communication device obtains the MAC address of the second communication device, and thereby unicasts a management frame to the second communication device according to the MAC address of the second communication device.